1. Field of the Invention
This invention relates to an apparatus and method for delivering energy to a tissue, and in particular to an apparatus and method for enhancing the detectability of a feedback signal from the treatment site. The feedback signal may be the result of stimulated emission of phosphors provided in a target or instrument present at the treatment site, or by reflection of an aiming or reference beams from the target or instrument. According to the present invention, an independently-generated aiming or reference beam, or a beam derived from the primary therapeutic beam, is encoded or modulated in such a way as to enhance detection of the feedback signal and to distinguish it from general background radiation. The encoded or modulated feedback signal may be detected by any detector or spectrometer capable of discriminating between different wavelengths, amplitudes, timing, frequency spectra, and so forth.
2. Description of Related Art
Hazardous conditions that can occur during surgical procedures involving lasers include overheating or burning of tissues or equipment at the energy-delivery or treatment site. Numerous systems have been developed to detect such overheating or burning, including systems that directly detect the glow emitted by burning tissue, as disclosed in U.S. Pat. No. 5,098,427, systems that detect radiation by utilizing the introducer as a waveguide for radiation originating from the treatment site, as disclosed in the inventor's U.S. Patent Publication No. 2007/0167937, and systems that provide a radiation or temperature detector at the treatment site, such as the system disclosed in the inventor's U.S. Patent Publication No. 2007/0049911.
In PCT Publication No. 2013/012986 and U.S. Patent Publication No. 2013/0218147, the inventor proposed inclusion in the feedback signal of stimulated emission or reflected signals having a discrete signature to enhance the detectability of the feedback signals. The stimulated emission or reflected signals provide information about conditions at the treatment site based on attenuation of the signal resulting from build-up of contaminants at a distal end of said optical fiber, and are more easily distinguishable from background radiation due to the unique signatures of the signals, which are to be distinguished from pyrolytic or temperature based emissions indicative of burning or the temperature of said treatment area.
Despite the unique signatures, however, detection of stimulated or reflected radiation, and in particular distinguishing the stimulated or reflected radiation from radiation resulting from the treatment itself, including radiation emitted by the tissues as they are heated, is still difficult. The present invention solves this problem by adding an encoder or modulator to the safety feedback system.
An example of a system to which the principles of the invention may be applied is illustrated in FIG. 1. FIG. 1 shows a pulsed infrared medical laser system of the type used for breaking kidney stones. The system shown in FIG. 1 includes a laser apparatus A1 for generating and supplying laser energy to fiber 30. The apparatus A1 includes a laser head and power supply L1 for producing a therapeutic laser beam having a desired wavelength λ1. A common laser apparatus for kidney stone applications is a Holmium laser that produces a wavelength of 2100 nm with up to 4 Joules of energy and a frequency as high as 50 Hz, although it will be appreciated that the invention may be applied to other types of laser systems, including lasers with a different output wavelength, energy, or frequency, and to applications other than kidney stone or other urological applications.
In the illustrated example, the primary Holmium laser beam λ1 is partially split by a beam splitter S1. Output power is regulated by a control feedback circuit such that a small percentage of the primary laser beam λ1 is directed and focused by lens assembly F1 into the photo-detector D1 and then analyzed by control circuit C1 in order regulate the power supply based on the feedback to ensure that the laser beam output has a predetermined wavelength, energy, and/or frequency. It will be appreciated by those skilled in the art that control circuit C1 may be an analog or microprocessor-based digital circuit, and that the present invention may be applied to systems with a variety of different types of laser power or output controller.
The remaining primary laser beam λ1 of the system illustrated in FIG. 1 is focused by lens assembly F3 into optical fiber 30, which carries the beam to the treatment site. The operator fires the laser by depressing an external foot switch FS1. The laser apparatus A1 also generates a secondary laser beam λ2 that is typically used as an aiming beam. The aiming beam λ2 may, by way of example, be generated by a relatively low powered diode laser L2 having a 5 milliwatt output that generates a visible light beam of, typically, 630 or 532 nanometers. The output from the laser diode L2 is collimated by a second lens assembly F2 and directed onto the beam splitter S1, which combines the aiming beam λ2 and primary beam λ1 and directs the combined beam to the lens assembly F3 for coupling into the optical fiber 30.